Marriott has their own homesharing platform to compete directly with Airbnb, but Marriott hotels list at Airbnb and not Marriott Homes & Villas, and in some cases pull their room inventory from Marriott entirely to sell suites through Airbnb.
What I find perhaps most striking is nobody at Marriott corporate thought to Google “airbnb+[Marriott brand]” to suss this stuff out?